IEEE 802.3ad Link Bundling

First Published: December 4, 2006

Last Updated: February 27, 2007

The IEEE 802.3ad Link Bundling feature provides a method of aggregating multiple Ethernet links into a single logical channel. This feature helps improve the cost effectiveness of a device by increasing cumulative bandwidth without requiring hardware upgrades. In addition, IEEE 802.3ad Link Bundling provides a capability to dynamically provision, manage, and monitor various aggregated links and enables interoperability between various Cisco devices and devices of third-party vendors.

This document describes how the IEEE 802.3ad Link Bundling feature leverages the EtherChannel infrastructure within Cisco IOS software to manage the bundling of various links.

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Gigabit EtherChannel

Gigabit EtherChannel is high-performance Ethernet technology that provides Gbps transmission rates. A Gigabit EtherChannel bundles individual Gigabit Ethernet links into a single logical link that provides the aggregate bandwidth of up to eight physical links. All LAN ports in each EtherChannel must be the same speed and all must be configured as either Layer 2 or Layer 3 LAN ports. Inbound broadcast and multicast packets on one link in an EtherChannel are blocked from returning on any other link in the EtherChannel.

When a link within an EtherChannel fails, traffic previously carried over the failed link switches to the remaining links within that EtherChannel. Also when a failure occurs, a trap is sent that identifies the device, the EtherChannel, and the failed link.

Port Channel and LACP-Enabled Interfaces

Each EtherChannel has a numbered port channel interface that, if not already created, is created automatically when the first physical interface is added to the channel group. The configuration of a port channel interface affects all LAN ports assigned to that port channel interface.

To change the parameters of all ports in an EtherChannel, change the configuration of the port channel interface; for example, if you want to configure Spanning Tree Protocol or configure a Layer 2 EtherChannel as a trunk. Any configuration or attribute changes you make to the port channel interface are propagated to all interfaces within the same channel group as the port channel; that is, configuration changes are propagated to the physical interfaces that are not part of the port channel but are part of the channel group.

The configuration of a LAN port affects only that LAN port.

IEEE 802.3ad Link Bundling

The IEEE 802.3ad Link Bundling feature provides a method for aggregating multiple Ethernet links into a single logical channel based on the IEEE 802.3ad standard. This feature helps improve the cost effectiveness of a device by increasing cumulative bandwidth without necessarily requiring hardware upgrades. In addition, IEEE 802.3ad Link Bundling provides a capability to dynamically provision, manage, and monitor various aggregated links and enables interoperability between various Cisco devices and devices of third-party vendors.

LACP supports the automatic creation of EtherChannels by exchanging LACP packets between LAN ports. LACP packets are exchanged only between ports in passive and active modes. The protocol "learns" the capabilities of LAN port groups dynamically and informs the other LAN ports. After LACP identifies correctly matched Ethernet links, it facilitates grouping the links into an EtherChannel. Then the EtherChannel is added to the spanning tree as a single bridge port.

Both the passive and active modes allow LACP to negotiate between LAN ports to determine if they can form an EtherChannel, based on criteria such as port speed and trunking state. (Layer 2 EtherChannels also use VLAN numbers.) LAN ports can form an EtherChannel when they are in compatible LACP modes, as in the following examples:

•A LAN port in active mode can form an EtherChannel with another LAN port that is in active mode.

•A LAN port in active mode can form an EtherChannel with another LAN port in passive mode.

•A LAN port in passive mode cannot form an EtherChannel with another LAN port that is also in passive mode because neither port will initiate negotiation.

LACP uses the following parameters:

•LACP system priority—You must configure an LACP system priority on each device running LACP. The system priority can be configured automatically or through the CLI. LACP uses the system priority with the device MAC address to form the system ID and also during negotiation with other systems.

•LACP port priority—You must configure an LACP port priority on each port configured to use LACP. The port priority can be configured automatically or through the CLI. LACP uses the port priority to decide which ports should be put in standby mode when there is a hardware limitation that prevents all compatible ports from aggregating. LACP also uses the port priority with the port number to form the port identifier.

•LACP administrative key—LACP automatically configures an administrative key value on each port configured to use LACP. The administrative key defines the ability of a port to aggregate with other ports. A port's ability to aggregate with other ports is determined by the following:

On ports configured to use LACP, it tries to configure the maximum number of compatible ports in an EtherChannel, up to the maximum allowed by the hardware. In Cisco IOS Release 12.2(31)SB2 on the Cisco 10000 series router, only 4 ports per bundle can be aggregated and the peer must be configured to support LACP. To use the hot standby feature in the event a channel port fails, both ends of the LACP bundle must support the lacp max-bundle command. See the "lacp max-bundle" section for additional details.

As a control protocol, LACP uses the Slow Protocol Multicast address of 01-80-C2-00-00-02 to transmit LACP protocol data units (PDUs). Aside from LACP, the Slow Protocol linktype is to be utilized by operations, administration, and maintenance (OAM) packets, too. Subsequently, a subtype field is defined per the IEEE 802.3ad standard [1] (Annex 43B, section 4) differentiating LACP PDUs from OAM PDUs.

RFCs

RFC

Title

No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.

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Command Reference

channel-group (interface)

To assign and configure an EtherChannel interface to an EtherChannel group, use the channel-group command in interface configuration mode. To remove the channel-group configuration from the interface, use the no form of this command.

Syntax Description

Integer that identifies the channel-group. Valid values are from 1 to 256; the maximum number of integers that can be used is 64.

For Fast EtherChannel groups, the number is an integer from 1 to 4. This number is the one previously assigned to the port-channel interface.

mode

Specifies the EtherChannel mode of the interface.

active

Enables Link Aggregation Control Protocol (LACP) unconditionally.

on

Enables EtherChannel only.

auto

Places a port into a passive negotiating state in which the port responds to Port Aggregation Protocol (PAgP) packets that it receives but does not initiate PAgP packet negotiation.

non-silent

(Optional) Used with the auto or desirable mode when traffic is expected from the other device.

desirable

Places a port into an active negotiating state in which the port initiates negotiations with other ports by sending PAgP packets.

passive

Enables LACP only when an LACP device is detected. This is the default state.

Command Default

No channel groups are assigned.

Command Modes

Interface configuration

Command History

Release

Modification

11.1CA

This command was introduced.

12.0(7)XE

Support for this command was implemented on Cisco Catalyst 6000 series switches.

12.1(3a)E3

The number of valid values for the number argumentwas changed; see the "Usage Guidelines" section for valid values.

12.2(2)XT

This command was implemented on the Cisco 2600 series, Cisco 3600 series, and Cisco 3700 series routers.

12.2(8)T

Support for this command was implemented on the Cisco 2600 series, the Cisco 3600 series, and the Cisco 3700 series routers and integrated into Cisco IOS Release 12.2(8)T.

12.2(14)SX

Support for this command was implemented on the Supervisor Engine 720.

12.2(17d)SXB

Support for this command on the Supervisor Engine 2 was integrated into Cisco IOS Release 12.2(17d)SXB.

12.2(18)SXE

This command was changed to support advanced QinQ translation on QinQ link bundles using GE-WAN interfaces on an OSM-2+4GE-WAN+ OSM on Cisco 7600 series routers.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2(31)SB2

This command was integrated into Cisco IOS Release 12.2(31)SB2.

12.2(33)SRB

Support for this command on the Cisco 7600 router was integrated into Cisco IOS Release 12.2(33)SRB.

Usage Guidelines

OSMs are not supported on Cisco 7600 series routers that are configured with a Supervisor Engine 32.

IP Address for the Physical Interface

You do not have to disable the IP address that is assigned to a physical interface that is part of a channel group, but Cisco highly recommends doing so.

Layer 2 and Layer 3 Port Channels

You can create both Layer 2 and Layer 3 port channels by entering the interfaceport-channel command or, when the channel-group gets its first physical interface assignment. The port channels are not created at run time, nor are they created dynamically.

You do not have to create a port-channel interface before assigning a physical interface to a channel group. A port-channel interface is automatically created when the channel group gets its first physical interface, if it is not already created.

Propagation of Configuration and Attribute Changes

Any configuration or attribute changes you make to the port-channel interface are propagated to all interfaces within the same channel group as the port channel. (for example, configuration changes are also propagated to the physical interfaces that are not part of the port-channel, but are part of the channel group.)

The on Keyword

When you use the on keyword, a usable EtherChannel exists only when a port group in on mode is connected to another port group in the on mode.

Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series Routers

You do not have to create a port-channel interface before assigning a physical interface to a channel group. A port-channel interface is created automatically when the channel group gets its first physical interface, if it is not already created.

Cisco Catalyst Switches

The number of valid values for number depends on the software release. For software releases prior to Cisco IOS Release 12.1(3a)E3, valid values are from 1 to 256; for Cisco IOS Release 12.1(3a)E3, 12.1(3a)E4, and 12.1(4)E1, valid values are from 1 to 64. Cisco IOS Release 12.1 E and later releases support a maximum of 64 values ranging from 1 to 256.

The channel-group number is global and is shared between all the channeling protocols. If a specific channel number is used for the PAgP-enabled interfaces of a channel group, that same channel number cannot be used for configuring a channel that has LACP-enabled interfaces or vice versa.

Entering the auto or desirable keyword enables PAgP on the specified interface; the command will be rejected if it is issued on an LACP-enabled interface.

The active and passive keywords are valid on PAgP-disabled interfaces only.

You can change the mode for an interface only if it is the only interface that is designated to the specified channel group.

The on keyword forces the bundling of the interface on the channel without any negotiation.

You can manually configure a switch with PAgP on one side and LACP on the other side in the on mode.

With the on mode, a usable EtherChannel exists only when a port group in on mode is connected to another port group in on mode.

If you enter the channel group command on an interface that is added to a channel with a different protocol than the protocol you are entering, the command is rejected.

If the interface belongs to a channel, the no form of this command is rejected.

All ports in the same channel group must use the same protocol; you cannot run two protocols on one channel group.

PAgP and LACP are not compatible; both ends of a channel must use the same protocol.

You can change the protocol at any time, but this change causes all existing EtherChannels to reset to the default channel mode for the new protocol.

Configure all ports in an EtherChannel to operate at the same speed and duplex mode (full duplex only for LACP mode).

All ports in a channel must be on the same DFC-equipped module. You cannot configure any of the ports to be on other modules.

On systems that are configured with nonfabric-enabled modules and fabric-enabled modules, you can bundle ports across all modules, but those bundles cannot include a DFC-equipped module port.

You do not have to create a port-channel interface before assigning a physical interface to a channel group. A port-channel interface is created automatically when the channel group gets its first physical interface, if it is not already created.

You do not have to disable the IP address that is assigned to a physical interface that is part of a channel group, but it is highly recommended.

You can create both Layer 2 and Layer 3 port channels by entering the interface port-channel command or when the channel group gets its first physical interface assignment. The port channels are not created at runtime or dynamically.

Any configuration or attribute changes that you make to the port-channel interface are propagated to all interfaces within the same channel group as the port channel (for example, configuration changes are also propagated to the physical interfaces that are not part of the port channel but are part of the channel group).

Only the on mode is supported when using this command with GE-WAN ports on the OSM-2+4GE-WAN+ OSM to create QinQ link bundles for advanced QinQ translation. Also, you cannot use the channel-group command on GE-WAN interfaces if MPLS is configured. You must remove all IP, MPLS, and other Layer 3 configuration commands before using the channel-group command with GE-WAN interfaces.

Note The GE-WAN interfaces on an OSM-2+4GE-WAN+ OSM behave slightly differently than other interfaces if you want to move the interface from one group to another. To move most other interfaces, you can enter the channel-group command again to delete the interface from the old group and move it to the new group. For GE-WAN ports, however, you must manually remove the interface from the group by entering the no channel-group command before assigning it to a new group.

For a complete list of guidelines, see the "Configuring EtherChannel" section of the Cisco 7600 Series Router Cisco IOS Software Configuration Guide.

Fast EtherChannel

Before you assign a Fast Ethernet interface to a Fast EtherChannel group, you must first create a port-channel interface. To create a port-channel interface, use the interfaceport-channel global configuration command.

If the Fast Ethernet interface has an IP address assigned, you must disable it before adding the Fast Ethernet interface to the Fast EtherChannel. To disable an existing IP address on the Fast Ethernet interface, use the no ip address command in interface configuration mode.

The Fast EtherChannel feature allows multiple Fast Ethernet point-to-point links to be bundled into one logical link to provide bidirectional bandwidth of up to 800 Mbps. Fast EtherChannel can be configured between Cisco 7500 series routers and Cisco 7000 series routers with the 7000 Series Route Switch Processor (RSP7000) and 7000 Series Chassis Interface (RSP7000CI) or between a Cisco 7500 series router or a Cisco 7000 series router with the RSP7000 and RSP700CI and a Cisco Catalyst 5000 switch.

A maximum of four Fast Ethernet interfaces can be added to a Fast EtherChannel group.

Caution The port-channel interface is the routed interface. Do not enable Layer 3 addresses on the physical
Fast Ethernet interfaces. Do not assign bridge groups on the physical Fast Ethernet interfaces
because it creates loops. Also, you must disable spanning tree.

To display information about the Fast EtherChannel, use the show interfaces port-channel EXEC command.

For more guidelines see the "Configuring EtherChannel" section of the Cisco 7600 Series Router Cisco IOS Software Configuration Guide and the "Configuring EtherChannel" section of the Catalyst 6500 Series Switch Cisco IOS Software Configuration Guide.

Examples

This example shows how to add EtherChannel interface 1/0 to the EtherChannel group that is specified by port-channel 1:

Router(config-if)# channel-group 1 mode on

Router(config-if)#

The following example shows how to add interface Fast Ethernet 1/0 to the Fast EtherChannel group specified by port-channel 1:

Router(config)# interface port-channel 1

Router(config-if)# exit

Router(config)# interface fastethernet 1/0

Router(config-if)# channel-group 1

Related Commands

Command

Description

interface

Creates a port-channel virtual interface and puts the CLI in interface configuration mode when the port-channelkeyword is used.

ip address

Sets a primary or secondary IP address on an interface.

show etherchannel

Displays the EtherChannel information for a channel.

show interfaces port-channel

Displays traffic that is seen by a specific port channel.

debug lacp

To enable debugging for all Link Aggregation Control Protocol (LACP) debug messages, use the debug lacp command in privileged EXEC mode. To disable all LACP debug messages, use the no form of this command.

debug lacp [all|event | fsm | misc | packet]

no debug lacp

Syntax Description

all

(Optional) Displays all LACP debug information.

event

(Optional) Displays all debug information relevant to events that occur within LACP.

fsm

(Optional) Displays changes within the LACP finite state machine.

misc

(Optional) Displays various debug information that may be useful for monitoring the status of LACP.

packet

(Optional) Displays the receiving and transmitting LACP control packets.

Command Default

LACP debugging activity is disabled.

Command Modes

Privileged EXEC

Command History

Release

Modification

12.1(13)EW

Support for this command was introduced on the Cisco Catalyst 4500 series switch.

12.2(31)SB2

This command was integrated into Cisco IOS Release 12.2(31)SB.

12.2(33)SRB

Support for this command on the Cisco 7600 router was integrated into Cisco IOS Release 12.2(33)SRB.

Usage Guidelines

This command is useful for troubleshooting problems with LACP.

Examples

The following sample output from the debug lacp allcommand shows a remote device removing a link:

lacp max-bundle

To define the maximum number of bundled Link Aggregation Control Protocol (LACP) ports allowed in a port channel, use the lacp max-bundle command in interface configuration mode. To return to the default settings, use the no form of this command.

lacp max-bundlemax-bundles

nolacp max-bundle

Syntax Description

max-bundles

Maximum number of bundled ports allowed in the port channel. Valid values are from 1 to 8.

Note On the Cisco 10000 series router, the valid values are from 1 to 4.

Defaults

The default settings are as follows:

•Maximum of 8 bundled ports per port channel.

•Maximum of 8 bundled ports and 8 hot-standby ports per port channel if the port channels on both sides of the LACP bundle are configured in the same way.

Command History

Support for this command was implemented on the Cisco 10000 series router and integrated into Cisco IOS Release 12.2(31)SB2.

12.2(33)SRB

Support for this command on the Cisco 7600 router was integrated into Cisco IOS Release 12.2(33)SRB.

Usage Guidelines

Cisco 10000 Series Router

This command requires a Performance Routing Engine 2 (PRE2) or PRE3.

Examples

This example shows how to set 3 ports to bundle in a port channel:

Router(config-if)# lacp max-bundle 3

Router(config-if)#

Related Commands

Command

Description

interface port-channel

Creates a port-channel virtual interface and puts the CLI in interface configuration mode.

ip address

Sets a primary or secondary IP address on an interface.

show etherchannel

Displays the EtherChannel information for a channel.

show interfaces port-channel

Displays traffic that is seen by a specific port channel.

lacp port-priority

To set the priority for a physical interface, use the lacp port-priority command in interface configuration mode. To return to the default setting, use the no form of this command.

lacp port-priority priority

no lacp port-priority

Syntax Description

priority

Integer from 1 to 65535 that indicates the priority for the physical interface. The default is 32768.

Command Default

The default port priority is set.

Command Modes

Interface configuration

Command History

Release

Modification

12.1(13)EW

This command was introduced on the Cisco Catalyst 4500 series switches.

12.2(14)SX

Support for this command on the Supervisor Engine 720 was integrated into Cisco IOS Release12.2(14)SX.

12.2(17d)SXB

Support for this command on the Supervisor Engine 2 was integrated into Cisco IOS Release12.2(17d) SXB.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2(31)SB2

This command was integrated into Cisco IOS Release 12.2(31)SB2.

12.2(33)SRB

Support for this command on the Cisco 7600 router was integrated into Cisco IOS Release 12.2(33)SRB.

Usage Guidelines

You must assign a port priority to each port on a device running Link Aggregation Control Protocol (LACP). You can specify the port priority by using the lacp port-priority command at the command-line interface (CLI) or use the default port priority (32768) that is carried as part of the LACP protocol data unit (PDU) exchanged with the partner. Port priority is used to decide which ports should be put in standby mode when a hardware limitation prevents all compatible ports from aggregating. Priority is supported only on port channels with LACP-enabled physical interfaces.

Note A high priority number means a low priority.

Port priority together with port number forms a port identifier.

Examples

This example shows how to set a priority of 23700 for an interface:

Router(config-if)# lacp port-priority 23700

Router(config-if)#

Related Commands

Command

Description

channel-group

Assigns and configures an EtherChannel interface to an EtherChannel group.

debug lacp

Enables debugging of LACP activities.

lacp system-priority

Sets the priority of the system.

show lacp

Displays information about LACP activities.

lacp system-priority

To set the priority for a system, use the lacp system-priority command in global configuration mode or in interface configuration mode. To return to the default setting, use the no form of this command.

lacp system-priority priority

no lacp system-priority

Syntax Description

priority

Integer from 1 to 65535 that indicates the priority for the system. The default is 32768.

Command Default

The default system priority is set.

Command Modes

Global configuration

Interface configuration

Command History

Release

Modification

12.1(13)EW

This command was introduced on the Cisco Catalyst 4500 series switches.

12.2(14)SX

Support for this command on the Supervisor Engine 720 was integrated into Cisco IOS Release12.2(14)SX.

12.2(17d)SXB

Support for this command on the Supervisor Engine 2 was integrated into Cisco IOS Release12.2(17d) SXB.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2(31)SB2

This command was integrated into Cisco IOS Release 12.2(31)SB2.

12.2(33)SRB

Support for this command on the Cisco 7600 router was integrated into Cisco IOS Release 12.2(33)SRB.

Usage Guidelines

You must assign a system priority to each device running Link Aggregation Control Protocol (LACP). You can specify the system priority by using the lacp system-priority command at the command-line interface (CLI) or use the default system priority (32768) that is carried as part of the LACP protocol data unit (PDU) exchanged with the partner. System priority is used with the MAC address of the device to form the system ID and also is used during negotiation with other systems. Priority is supported only on port channels with LACP-enabled physical interfaces.

Note A high priority number means a low priority.

The lacp system-priority command can also be issued in interface configuration mode. After you enter the command, the system returns to global configuration mode.

Examples

The following example shows how to set a system priority of 25500 for a device:

Router(config)# lacp system-priority 25500

Related Commands

Command

Description

channel-group

Assigns and configures an EtherChannel interface to an EtherChannel group.

debug lacp

Enables debugging of LACP activities.

lacp port-priority

Sets the priority of a port.

show lacp

Displays information about LACP activities.

show lacp

To display Link Aggregation Control Protocol (LACP) information, use the show lacp command in user EXEC or privileged EXEC mode.

Syntax Description

(Optional) Number of the channel group; valid values are from 1 to 282.

counters

Displays information about the LACP traffic statistics.

detail

(Optional) Detailed internal information.

internal

Displays LACP internal information.

neighbors

Displays information about the LACP neighbor.

sys-id

Displays the LACP system identification. It is a combination of the port priority and the MAC address of the device

Defaults

This command has no default settings.

Command Modes

User EXECPrivileged EXEC

Command History

Release

Modification

12.2(14)SX

Support for this command was introduced on the Supervisor Engine 720.

12.2(17d)SXB

Support for this command on the Supervisor Engine 2 was extended to Cisco IOS Release 12.2(17d)SXB.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2(31)SB2

This command was integrated into Cisco IOS Release 12.2(31)SB2.

12.2(33)SRB

Support for this command on the Cisco 7600 router was integrated into Cisco IOS Release 12.2(33)SRB.

Usage Guidelines

Use the show lacp command to troubleshoot problems related to LACP in a network.

If you do not specify a channel-group, all channel groups are displayed.

Thechannel-group values from 257 to 282 are supported on the CSM and the FWSM only.

You can enter the optional channel-group to specify a channel group for all keywords, except the sys-id keyword.

Examples

show lacp sys-id Example

This example shows how to display the LACP system identification using the show lacp sys-id command:

Router> show lacp sys-id

8000,AC-12-34-56-78-90

The system identification is made up of the system priority and the system MAC address. The first 2 bytes are the system priority, and the last 6 bytes are the globally administered individual MAC address that is associated to the system.

LACP Statistics for a Specific Channel Group Examples

This example shows how to display the LACP statistics for a specific channel group:

Router# show lacp 1 counters

LACPDUs Marker LACPDUs

Port Sent Recv Sent Recv Pkts Err

---------------------------------------------------

Channel group: 1

Fa4/1 8 15 0 0 3 0

Fa4/2 14 18 0 0 3 0

Fa4/3 14 18 0 0 0

Fa4/4 13 18 0 0 0

The output displays the following information:

•The LACPDUs Sent and Recv columns display the LACPDUs that are sent and received on each specific interface.

Feature Information for IEEE 802.3ad Link Bundling

Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Note Table 4 lists only the Cisco IOS software release that introduced support for a given feature in a given Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS software release train also support that feature.

Table 4 Feature Information for IEEE 802.3ad Link Bundling

Feature Name

Releases

Feature Information

IEEE 802.3ad Link Bundling

12.2(31)SB212.2(33)SRB

The IEEE 802.3ad Link Bundling feature provides a method for aggregating multiple Ethernet links into a single logical channel based on the IEEE 802.3ad standard. In addition, this feature provides a capability to dynamically provision, manage, and monitor various aggregated links and enables interoperability between various Cisco devices and devices of third-party vendors.

In 12.2(31)SB2, this feature was implemented on the Cisco 10000 series router.

In 12.2(33)SRB, this feature was implemented on the Cisco 7600 router.

Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and coincidental.